This application is related to the concurrently filed Angarola et al. applications, Ser. Nos. 820,210, 820,162, and 820,163, entitled, respectively, "Dunnage Bag Inflation Air Gun," "Apparatus for Rapidly Inflating and Pressurizing a Dunnage Bag," and "Dunnage Bag Fill Valve."
This invention relates to dunnage bags for use in shipment of freight by rail, ship, truck, aircraft, and the like, and more particularly to inflatable, disposable dunnage bags for such use. Dunnage bags may be reusable, and if reusable, are usually made of single or multiple plies of rubber, plastic, or fabric. Alternatively, dunnage bags may be disposable. Typically, such disposable dunnage bags have a gas-tight bladder (usually polyethylene) surrounded by an outer protective and supportive shroud consisting of one or more plies of material, usually heavy paper. The inflatable, disposable dunnage bags are used in freight carriers where it is customary to fill the spaces between the cargo, or between the cargo and the walls of the freight carrier, to prevent the cargo from shifting and damaging either the cargo itself and/or the walls of the freight carrier. Inflatable, disposable dunnage bags are placed between the cargo in a deflated condition and are subsequently inflated with a gas, usually air, to a certain design pressure, typically between 1 and 8 pounds per square inch gauge, dependent on the size and wall structure of the particular bag.
Experience with this type of dunnage bag has revealed certain difficulties during inflation. First, in the United States, such dunnage bags are normally inflated with high pressure air nozzles through a valve in the side of the bag. The valves most commonly used are of the well-known Schrader type which are relatively small, having an exterior diameter of about 9/16 inch. These valves typically have a helical spring to bias a valve stem or plug against a relatively small internal orifice, usually between one-sixteenth and five-sixteenths inch in diameter. The valve housing is typically constructed of polyethylene which can be heat-sealed to the dunnage bag bladder to form an airtight connection. However, the valve stem is typically plastic or metal and the biasing spring is typically constructed from metal, such as steel. It would be desirable to provide a method of dunnage bag inflation that could be used with a more simplified valve design.
Typically, dunnage bags are inflated with high pressure air in the range of between 30 and 120 pounds per square inch gauge. Thus, unless the inflation time or air pressure is carefully regulated (as by means of a pressure regulating device near the discharge of the air hose), it is quite easy to pressurize a bag beyond the design, or allowable, pressure and to thereby rupture the bag and possibly damage the cargo and/or carrier. Thus, it would be desirable to provide a method of inflation using a gas such as air to effect the filling of such dunnage bags without the danger of overpressurization.
It has been suggested that low pressure air could be used to fill dunnage bags. However, the use of low pressure air, by itself, has a number of drawbacks. First, the time required to fill a dunnage bag through the small internal orifice of the Schrader type valve in use today would be much longer than the time required to fill a dunnage bag when using high pressure air. Also, a dunnage bag can still be overpressurized and ruptured (which may damage the cargo) when using low pressure air unless the "low" pressure is adjusted low enough for the particular dunnage bag. Thus, in situations where a number of different sizes of dunnage bags (having different design fill pressures) are to be inflated with the same low pressure air supply, the low pressure air supply pressure would still have to be carefully regulated to accommodate each different bag being filled. To overcome these drawbacks, it would be desirable to provide a method for filling different design pressure dunnage bags with pressurized air relatively rapidly and to provide a means for self-limiting the maximum pressure to which the dunnage bag could be filled.
Another problem encountered with the filling of inflatable dunnage bags results from the fact that such bags are filled after they have been placed and positioned between cargo or between the walls of the freight carrier and the cargo. Consequently, there are many times when access to the fill valve on the dunnage bag is extremely limited. In those instances, there is very little clearance area around a fill valve and this precludes the use of large, elongated gun-type air injection mechanisms that stick out a number of inches from the top of the valve during inflation. Consequently, it would be desirable to provide a method for inflating dunnage bags which would not require apparatus that projects a relatively great distance from the exterior surface of the bag.